Im about to drop 5000 dollars on an engraving machine to engrave btc public private key pairs. one with an address and one with a private key (youd get 2 cards). if someone on the street wants to pay you, you give em the public card to scan (or type). put the private 1 in a safe and redeem it when you need to. This would be probably the safest way to store btc since the network will hold it and you need not rely on your computer or any electronic form of storage. you can also easily check the card balance by going to block explorer.

the cards would cost approx $20 in btc. I have a fairly high amount of trust and would make keypairs on a machine disconnected from the internet solely for this purpose. the pairs would be deleted after each one is made and memory wiped frequently with some sort of erasing program that erases rewrites and erases again.